- Over analyzing? I thought the "compromised" shaft strength and the shorter screw engagement needed analysis, and so did you.
- Yes, I know porting has been around for decades and w/o tune. But you were concerned w/ that, despite proving satisfactory for so long.
- Erratic idle and off idle are not there, ask the people testing it, they'll tell you.
- I have no problem w/ the bumps, the problem is the smooth ellipsoidal contour adjacent to it. Please read the thread and try to understand it, also read the original patent for S-Type throttle bodies by Nissan 1987.
- Fuel flow is being compensated accurately by the ECM. I'm getting the all the right ratios where they should be. We don't need tuning.
- Throttle Switch; on/off? This is exactly what you are proposing w/ the tune.
- Please read the service manual, the ECM can compensate for manufacturing variations, it can even compensate w/o the MAF sensor, juts by calculating from MAP sensor, inlet air temp sensor and RPM. As long as the modification occurs within the limits of ECM compensation, no tune is needed.
- You are thinking of times when MAF sensors were very expensive and the air was metered by the throttle blade.

If you don't own a C7 or a Corvette at all, then you don't exactly know what we are talking about. Yes, I'm a Corvette guy and so are most people in this forum. Please, let us leave this aside. This is exactly where we don't want this thread to go.

You realize I'm the only real "tuner" that's poked a stick in here? The guys on this forum that understand tuning wouldn't waste their time trying to enlighten somebody that thinks "tuning isn't needed". Are you kidding? Tuning is vital.Why don't you go over to the HPTuners forum and ask them if tuning is needed for what you're changing. Or better yet, is tuning the proper "fix" for this issue and is easier and with less side effects than this hardware change. Ask the experts that question and see what they say.

Quote:

Fuel flow is being compensated accurately by the ECM. I'm getting the all the right ratios where they should be. We don't need tuning.

And how exactly do you know this? Do you have logs showing fueling? Please elaborate on this statement, I'd really like to know how you can make a statement like that. What exactly are the "right ratios"?

And as far as your "Testing", has a single person you've given one of your throttle bodies to actually LOGGED the changes? Or are they (don't make me mention the C7 demographics) giving you feedback by what their "butt dyno" tells them? Again, are you kidding? What kind of feedback is that? You pride yourself on all the technical analyzing, but your testing relies on what somebody might "feel"???

How about this... We take a car and "fix" the tune. Have 10 people drive it. Then take the same car and put your TB on it with the stock tune. Have 10 people drive it again. I know what the results would be, they'd be all over the board because no sane Engineer or tuner or whatever would use random people's butt dyno for accurate testing. Now let's take that same car and LOG the results of your TB. Now that I'd like to see. If you truly crave knowledge wouldn't you also want to see the same data?

Or you can keep trying to silence my voice of experience, training and knowledge on this subject specifically. Then NOBODY learns. And how on earth do you have any idea what cars I own or have owned? Who's doing the "speculating" here?

@gmtech16450yz, Not speculating. I've read your previous posts on other threads, and you said you don't have a Corvette, that's all I can say. Oh, no corvette guy calls others a corvette guy, that was a reinforcing hint.

Since your first post, I have addressed all your concerns (tuning vs. TB mod, half-shaft, screws) then you switched to something else which I have also answered, then yet another change of subject to logging and test methods. Yes, I'm logging AFR; what's the next issue you'll ask about? I can see where this is going and it will have no end. I have everything that is needed to make this project successful. I have shared here way more than it would be prudent for a vendor and I can't afford to spend more time on this.

Quote:

Originally Posted by gmtech16450yz

Or you can keep trying to silence my voice of experience, training and knowledge on this subject specifically.

I’d like to reassure you, and more importantly members w/ a genuine interest for this modification, that the main contributors to this design are engineers w/ great academic and empirical backgrounds, also with decades of experience in the fields of aerospace, mechanical, electro-mechanical, design, and materials. I can also tell you that this is not the first butterfly valve we have worked on, neither it is the most critical one.

A buddy of mine told me about this thread. Sorry but I read a little bit of it and lol'd quite a bit! The truth of this situation is you're looking in the wrong place to fix this "problem". These GM throttle bodies can and do move as fast or faster than your foot. I say faster because they can literally go full throttle AHEAD of your foot movement.

My buddy has a '16 C7 Z51. He said his car has done this throttle/pedal lag thing since he got it. He drove over and we logged it. I ALWAYS log the relationship between pedal and throttle, many "tuners" don't. If you don't log these two parameters, you won't have any idea of what's going on. Pedal/throttle relationship is one of the most basic tuning/driveability aspects, it literally determines how the engine feels when your foot moves. (Side note... For those that wish for the days of cable throttles, electric throttles can do everything a cable can, and many things a cable CAN'T. Throttle by wire is one of the best things to happen to engine management.)

So no surprise, the throttle mapping in the stock ECM calibrations lags behind pedal movement. This is done for many reasons- better traction, longer driveline life, lower emissions and of course passenger comfort. His C7 did have quite the lag though, I took screen shots of when he jabbed the pedal quickly and the engine almost didn't even react. I could see plain as day the throttle mapping was WAY behind the pedal, it should be obvious in these pictures. I had him pull over, I looked at his tune and changed a few things. Loaded the tune and in the first 2 minutes of driving he could tell it was fixed. The lag was COMPLETELY GONE. I could see it in the log, throttle plate movement was following pedal movement very closely. One tune, 5 minutes, fixed. The funniest part? He said he was going to have to "relearn" how to blip the throttle on downshifts (M7, not using rev-match) because the throttle response was so much quicker and higher.

My advice? Find a reputable tuner and have them fix it for you. It's 100% "fixable" in the tune, it's something any decent "tuner" should know how to do. Changing the throttle body, modifying the throttle body or using an aftermarket throttle body are all NOT fixes for this issue. They will NOT make the lag go away. The lag is built into the engine calibrations.

Here are the screen shots. (Sorry I didn't put the cursor at the actual spots, it should still be super apparent even without seeing the values though. It's really as simple as this- before tune- Blue over Yellow, after tune- Yellow over Blue. lol.) First 3 shots are of the stock calibrations. Blue trace is the pedal position, Yellow trace is the throttle position. Clearly you can see the throttle is lagging well behind the pedal and isn't going even half as high percentage wise...

These are the after tune shots. As you can see, the throttle is opening quicker and in several cases, higher than pedal percentage. In the zoomed in shot you can see the throttle plate actually moved FASTER than the pedal movement....

You realize I'm the only real "tuner" that's poked a stick in here? The guys on this forum that understand tuning wouldn't waste their time trying to enlighten somebody that thinks "tuning isn't needed". Are you kidding? Tuning is vital.Why don't you go over to the HPTuners forum and ask them if tuning is needed for what you're changing. Or better yet, is tuning the proper "fix" for this issue and is easier and with less side effects than this hardware change. Ask the experts that question and see what they say.

And how exactly do you know this? Do you have logs showing fueling? Please elaborate on this statement, I'd really like to know how you can make a statement like that. What exactly are the "right ratios"?

And as far as your "Testing", has a single person you've given one of your throttle bodies to actually LOGGED the changes? Or are they (don't make me mention the C7 demographics) giving you feedback by what their "butt dyno" tells them? Again, are you kidding? What kind of feedback is that? You pride yourself on all the technical analyzing, but your testing relies on what somebody might "feel"???

How about this... We take a car and "fix" the tune. Have 10 people drive it. Then take the same car and put your TB on it with the stock tune. Have 10 people drive it again. I know what the results would be, they'd be all over the board because no sane Engineer or tuner or whatever would use random people's butt dyno for accurate testing. Now let's take that same car and LOG the results of your TB. Now that I'd like to see. If you truly crave knowledge wouldn't you also want to see the same data?

Or you can keep trying to silence my voice of experience, training and knowledge on this subject specifically. Then NOBODY learns. And how on earth do you have any idea what cars I own or have owned? Who's doing the "speculating" here?

Most of us don't want a tune because it will automatically void the warranty. Why is that so hard for you to understand? Quit trolling pal and leave the thread to those of us who are truly interested. Maybe you can go work on your Mustang instead....

Sorry, that was kind of a smart *** response. I couldn't resist though.

No, a tune isn't necessarily a "warranty buster".

How many threads are on this forum where someone bought a used C7, drove it a while, had an engine failure and had their warranty denied because the car had been tuned? Why is it that every tuner says a tune won't void your warranty when it is a well known fact it does? You gain credibility when you tell the truth and diligently try to be open, as Mike has done here. Coming in and posting known lies doesn't make you credible in the very least.

Most of us don't want a tune because it will automatically void the warranty.

I know your post wasn't for me, but he isn't "trolling" he is just disclosing some facts about what actually causes the issue so many want to prevent. There are plenty of threads about throttle bodies and plenty of reviews that say "It helped but didn't solve" which is pure post purchase justification when the problem remains. I am not saying tune your car because I understand many are risk averse and that's fine you have to do what you can within your limits. I am just saying that he isn't wrong, there are several places in the engine calibration that absolutely kill off idle and initial tip in at low speeds only. Spark timing, cam timing, torque model, etc. All that will be the same even if you change your throttle body.

Quote:

Originally Posted by DWillys

How many threads are on this forum where someone bought a used C7, drove it a while, had an engine failure and had their warranty denied because the car had been tuned? Why is it that every tuner says a tune won't void your warranty when it is a well known fact it does? You gain credibility when you tell the truth and diligently try to be open, as Mike has done here. Coming in and posting known lies doesn't make you credible in the very least.

In all the C7 forums for the last 13 months (got bored searching) I found 3 threads about a "surprised owner with a tuned ECM and a blown engine." There have been what, 155,000+ C7's produced? Let's not pretend like a blown tuned C7 warranty denial situation is a thing. I know, "not everyone is on corvette forum," however the point remains.

My point is don't get discouraged and upset because someone is raining on your new hope, just go in with open eyes, that's all gmtech is providing.
It would be really great if the OP solved the issue with a throttle body modification, he would introduce something no one has before, I hope it works well and after the initial wave of anecdotes and placebo effects the reviews keep coming in about a decisive and conclusive fix.

My point is don't get discouraged and upset because someone is raining on your new hope, just go in with open eyes, that's all gmtech is providing.
It would be really great if the OP solved the issue with a throttle body modification, he would introduce something no one has before, I hope it works well and after the initial wave of anecdotes and placebo effects the reviews keep coming in about a decisive and conclusive fix.

Thanks Higgs, I agree 100%. My main concern w/ gmtech's post were; his burlesque tone, the horrific conclusions he arrived at, and the complete dismissal of a viable (proven to some extent so far) solution. It needed to be addressed. The delay is a compounded problem, no doubt. Nevertheless, I firmly believe the main contributor is a throttle body geometry purposely shaped to achieve the 29 mpg in a 6.2 L engine, and that a tune or a TC can do very little in that regard.

There should not be placebo here, I'm promising numbers, not adjectives. It either doubled the slope of the OEM curve (+ others) at part throttle right off idle or it didn't. Anyone w/ minimal logging/streaming capabilities should be able to measure that. If someone doesn't have the instruments to measure it, the'll feel a stark difference that will leave no doubt. I'd say if someone have to think, or try again to determine whether it made a difference, then say "it didn't".

I know it's 2019 and we are all liberals now but let's not forget we are car men around here and we drink motor oil and take care of our diaper rash with white lithium and we love the smell of race gas in the morning. I think we should all be mean to each other and drink beer over bloody noses. ;-)

An aftermarket tune isn't nearly as obvious to dealer techs as screws from a modified throttle plate stuck in the tops of your pistons would be. lol.

However, if you blow the engine the first thing GM is going to do is ask to see the ECM tune state. That is when they will say not covered.

The problem is exaggerated vastly. I get an intermittent hesitation every now and then when taking off from a stop. However, it is easily avoided if I follow the instructions provided at Spring Mountain which were to release the clutch and as the car starts to move add a little throttle and then once the clutch is all the way out add more throttle. When I remember to do that I never get that little hesitation. As for a stumble while driving I run around town in 5th and 6th gear all the time with rpms between 1000 and 1500 and never get a stumble when I add throttle. If I put the car in Eco mode I will hear the exhaust change when the engine switches between V8 and V4 mode as the exhaust is always closed in V4 mode.